Crystals of superconducting Mo$_{ 8}$Ga$_{ 41}$ ($T_{ \text{ c}}=9.8$ K) and Mo$_{ \text{ 8-x}}$V$_{ \text{ x}}$Ga$_{ 41}$ limited solid solution $(x_{ \text{ max}}=1.9(2))$ have been grown from the high-temperature Ga flux and confirmed to have the V$_{ 8}$Ga$_{ 41}$ type of crystal structure at room temperature. Thermodynamic and transport measurements as well as electronic structure calculations were performed to investigate both normal- and superconducting-state properties of Mo$_{ 8}$Ga$_{ 41}$. The discontinuity in the heat capacity at $T_{ \text{ c}}$, $\Delta{ }c_{ \text{ p}}/\gamma_{ \text{ N}}T_{ \text{ c}}=2.83$ in zero magnetic field, indicates a much stronger electron-phonon coupling than in the standard BCS limit. From the heat capacity data, we estimated the electron-phonon coupling constant $\lambda_{ \text{ ep}}=0.9$. The upper critical field is $\mu_{ 0}H_{ \text{ c2}}(0)=8.3$ T, while the lower one is only $\mu_{ 0}H_{ \text{ c1}}(0)=131$ Oe. The upper critical field of Mo$_{ 8}$Ga$_{ 41}$ exhibits a clear enhancement with respect to the Werthamer-Helfand-Honenberg prediction, consistent with the strong electron-phonon coupling. The Mo$_{ \text{ 8-x}}$V$_{ \text{ x}}$Ga$_{ 41}$ limited solid solution also exhibits superconducting properties, and the critical temperature $T_{ \text{ c}}$ is reduced only slightly with increasing $x$.
Categories: cond-mat.supr-con